Defra Research Project Final Report for WU0101 – Opportunities for reducing water use in Agriculture
(project ended 30 November 2006)
Defra Project WU0101
Opportunities for Reducing Water use in Agriculture
Dr Andrew J. Thompson1
Dr John A. King2
Dr Ken A. Smith2
Don H. Tiffin2
1. Warwick HRI, University of Warwick, Wellesbourne, Warwick, Warwickshire,CV35 9EF. http://www2.warwick.ac.uk/fac/sci/whri/research/plantwateruse/
2. ADAS, Woodthorne, Wergs Road, Wolverhampton, WV6 8TQ. http://www.adas.co.uk/
June 2007
Executive Summary
Aims and objectives
The aim of this study was to identify new and existing areas of research and knowledge transfer that will create opportunities for reducing water use in English and Welsh agriculture. The objectives were as follows:
· To identify geographical regions and agricultural sectors where research and knowledge transfer activities have the potential to lead to significant reductions in water use
· To review current and emerging technologies aimed at saving water in agriculture
· To review existing initiatives and case studies related to saving water in agriculture
· To identify and prioritise research areas and to seek consensus from an expert group
Summary of findings
The aim of reducing water inputs in agriculture is two-fold: to protect water courses from ecological damage, and to sustain the rural economy. Agriculture has an absolute need to use water to produce crops and livestock and in many horticultural crops product quality and profitability are highly dependent on timing, uniformity and volume of water applied. However, water availability is declining. Where water is “available”, in the sense that its use does not damage the environment, an increase in water use will often improve productivity and the success of agricultural enterprises. Any water saving measures need to be targeted to catchments where water is in short supply and environmental benefits can be realised.
· The UK relies heavily on imports of agricultural products and is a major net importer of “virtual water”. For reasons of food security we should seek to maximise our own agriculture outputs using our available water resources and to make significant contributions to the global research effort to increase the efficient and sustainable use of water in agriculture overseas.
· The Anglian, Southern and Thames Environment Agency regions are clearly the priority regions where most benefits can be realised from reducing water use in agriculture. The Anglian region is dominant as it is by far the largest abstractor of water for irrigation of field crops, where peak demand for water occurs during periods when water availability is lowest.
· In livestock farming In England and Wales most of the water use is for drinking, particularly for dairy cows, with little scope for savings. In addition, although direct water abstractions for agriculture are approximately equally divided between livestock and crop production, the livestock industry is more prominent in the West where rainfall is higher and pressure on water supplies is less than in the East. However, significant water savings can still be made by reducing waste during farm washing procedures as this makes up some 21% of water used for dairy cows, and further savings can be made through good management practices at the farm scale.
· Field crops in the UK are either exclusively rain fed, or they receive supplementary irrigation. Abstraction of water for irrigation can clearly reduce levels of ground water and surface flows, but it is also true that changing land use to crops with higher evapotranspiration, such as anticipated with biomass crops, even if they are not irrigated, can also have a big impact on local hydrology; further research is needed to model land use effects. Most water abstractions are applied to potato and vegetable crops, with around half of the water abstractions for field crops being applied to potato. Of this, about half the irrigation for potato crops is used to control common scab, and if non-irrigation-based methods could be developed to this end then large water savings could be achieved. The other half of the water applied to potatoes is required for optimising tuber yield. Breeding research is justified in potato because it is a large, single-species sector; key breeding targets are resistance to common scab, and an improved root system. Agronomy research to promote good soil management and to reduce soil compaction for potato could significantly reduce the need for irrigation. In field vegetables, further research is required to establish the levels of water deficit that are acceptable to maintain quality and yield for each combination of crop and soil type, and irrigation scheduling research could make gains by combining low cost technologies for sensing environmental variables (e.g. thermography, soil sensors, potential evapotranspiration sensors) with mobile communications and automation. Improvements in models for scheduling, particularly for the relationships between soil type, soil water movement and root zone development would be beneficial. Currently, a significant proportion of irrigators do not use scientific methods for irrigation scheduling but rely on personal experience and judgment; significant water savings could be made by improving the uptake of existing technology. Efforts to form networks of Farmer-Organised Abstractor Groups should be supported to encourage the spread of best practice and joint investment, for example in on-farm reservoirs.
· Intensive soft-fruit production under polythene is an expanding industry that uses significant amounts of irrigation water. There are opportunities for saving water through the use of regulated deficit irrigation, improved scheduling and breeding. In general, although crop production in polytunnels is intensive and can create local problems it does use water more efficiently than open field crops, and as water availability declines, more growers may move to polytunnels or protected cropping to maximise returns from available water.
· Hardy nursery stock (HNS) is a major user of water for irrigation and although water costs are a minor consideration in the industry, improvements in irrigation methods and scheduling could reduce labour costs, improve product quality and reduce water inputs. Knowledge transfer activities to promote investment in sub-irrigation systems, rain water harvesting and recycling systems could lead to substantial water savings.
· The key to successful breeding programs to increase water use efficiency and drought resistance is the understanding and modelling of the physiological traits that limit productivity in each crop and in each environment where it is grown. This will allow trait selection assays to be developed that are useful to breeders but it will require commercial breeders and scientists to work closely together, supported by public funding. Genetic modification using candidate genes should focus on moving work from model species to crop species and on the evaluation of field performance at an early stage through multidisciplinary collaboration. In addition to potato, breeding efforts are needed for the non-irrigated, large-acreage crops comprising cereals, oilseed rape, sugar beet and biomass crops in order to improve yield stability as drought years become more frequent. Research is also needed to establish if alternative (e.g. Mediterranean) crops could be adapted to Southern England as climate change progresses.
A list of research priorities and estimates of potential water savings are given in Table 8 of the Project Report.
Contents
1. Aim……………………………………………………………………………………………………… 8
2. Objectives……………………………………………………………………………………………… 8
3. Introduction…………………………………………………………………………………………….. 8
3.1. Pressures on water for agriculture……………………………………………………………………. 8
3.2. Drivers for water saving: why reduce water use in agriculture? ………………………………….. 9
3.3. A global perspective – water, food security and sustainable agriculture…………………………. 9
3.3.1. Dependence on imported embedded water………………………………………………... 9
3.3.2. Global research agenda……………………………………………………………………... 10
3.4. Consumption of water by agriculture in England and Wales: the water cycle and CAMS……… 10
4. Identification of sectors and geographical regions where research and knowledge transfer activities have the potential to lead to significant reductions in water use……………………… 12
5. Water use in crop production - generic approaches and issues………………………………… 14
5.1. Water use efficiency: definitions and scales………………………………………………………… 14
5.1.1. Catchment scale……………………………………………………………………………… 14
5.1.2. Farm scale…………………………………………………………………………………….. 14
5.1.3. Field scale……………………………………………………………………………………… 14
5.1.4. Plant scale…………………………………………………………………………………….. 14
5.1.5. Leaf scale……………………………………………………………………………………… 15
5.2. Irrigation scheduling……………………………………………………………………………………. 15
5.2.1. Methods and equipment for applying water……………………………………………….. 15
5.2.2. Approaches to monitoring need for irrigation………………………………………………. 15
5.2.2.1. Soil water monitoring……………………………………………………………... 15
5.2.2.2. Direct monitoring of the crop…………………………………………………….. 16
5.2.2.3. Models using meteorological and crop development data and the potential of remote sensing………………………………………………………………… 16
5.3. Crop improvement……………………………………………………………………………………… 17
5.3.1. Defining terms: water use, water use efficiency, drought resistance and yield potential………………………………………………………………………………………… 17
5.3.2. Drought resistance can incur a penalty…………………………………………………….. 17
5.3.3. Strategies for improving drought resistance that minimise penalties in yield potential... 18
5.3.4. Breeding for drought resistance must tailor crop water use to demand based on crop type, phenology and environment…………………………………………………………… 19
5.3.5. Breeding for drought resistance: key points……………………………………………….. 19
6. Specific crop sectors………………………………………………………………………………….. 20
6.1. Field crops: Potato (Solanum tuberosum subsp. tuberosum)...... 20
6.1.1. Summary agronomic data……………………………………………………………………. 20
6.1.2. Physiology and agronomy of water use……………………………………………………. 21
6.1.3. Irrigation and common scab (Streptomyces spp.)………………………………………… 22
6.1.4. Irrigation scheduling for potato……………………………………………………………… 22
6.1.5. Agronomy and cultural practices……………………………………………………………. 23
6.1.6. Conclusions: Water saving in the potato crop through agronomy and physiology……. 24
6.1.7. Water saving through crop improvement in potato……………………………………….. 24
6.1.7.1. Is crop improvement for water use traits in potato worthwhile? ……………….. 24
6.1.7.2. Introduction to potato genetics…………………………………………………….. 24
6.1.7.3. Genetic diversity…………………………………………………………………….. 25
6.1.7.4. Conventional breeding……………………………………………………………… 25
6.1.7.5. The potential role of Marker Assisted Selection (MAS) in breeding for drought resistance…………………………………………………………………………….. 26
6.1.7.5.1. Two-parent mapping populations……………………………………… 27
6.1.7.5.2. Association mapping……………………………………………………. 27
6.1.7.5.3. Current use of molecular markers and potential use to select for drought resistance………………………………………………………. 27
6.1.7.5.4. Genome sequencing projects and comparative genomics in Solanum………………………………………………………………….. 28
6.1.7.6. How to assess WUE and drought resistance of cultivars, or within a breeding program………………………………………………………………………………. 28
6.1.7.6.1. Root traits………………………………………………………………… 28
6.1.7.6.2. Canopy development…………………………………………………… 29
6.1.7.6.3. Use of stable isotope techniques……………………………………… 29
6.1.7.7. Genetic Manipulation…………………………………………………………….. 30
6.1.7.8. Conclusions: water saving through crop improvement in potato……………. 31
6.2. Field crops: vegetables ……………………………………………………………………………….. 31
6.2.1. Background information……………………………………………………………………… 31
6.2.2. Irrigation scheduling………………………………………………………………………….. 32
6.2.3. Mulching……………………………………………………………………………………….. 32
6.2.4. Breeding……………………………………………………………………………………….. 32
6.2.5. Conclusions: water saving in field vegetables…………………………………………….. 33
6.3. Field crops: Sugar beet (Beta vulgaris spp. vulgaris) ……………………………………………… 33
6.3.1. Background information……………………………………………………………………… 33
6.3.2. Research opportunities………………………………………………………………………. 33
6.3.3. Conclusions: water saving for sugar beet………………………………………………….. 34
6.4. Field crops: Fruit……………………………………………………………………………………….. 34
6.4.1. Background information……………………………………………………………………… 34
6.4.2. Water use in strawberries (Fragaria x ananassa)…………………………………………. 34
6.4.3. Strawberry breeding………………………………………………………………………….. 35
6.4.4. Irrigation scheduling in soft fruit……………………………………………………………... 35
6.4.5. Rain water collection from polytunnels and water recycling……………………………… 35
6.4.6. Orchard fruit…………………………………………………………………………………… 36
6.4.7. Conclusions: water savings in field-grown fruit …………………………………………… 36
6.5. Field crops: Cereals…………….……………………………………………………………………... 36
6.5.1. Conclusions: Water saving for cereals……………………………………………………… 37
6.6. Field crops: Energy crops……………………………………………………………………………… 37
6.6.1. Background……………………………………………………………………………………. 37
6.6.2. Crops for bioethanol, biobutanol and biodiesel production………………………………. 37
6.6.2.1. Production trends…………………………………………………………………. 37
6.6.2.2. Water use………………………………………………………………………….. 37
6.6.3. Biomass crops………………………………………………………………………………… 38
6.6.3.1. Production trends…………………………………………………………………. 38
6.6.3.2. Water use and hydrology………………………………………………………… 38
6.6.4. Breeding for WUE in energy crops…………………………………………………………. 38
6.6.5. Conclusions: energy crops…………………………………………………………………… 39
6.7. Protected crops (edibles and ornamentals)…………………………………………………………. 39
6.7.1. Background information……………………………………………………………………… 39
6.7.2. Which is the best source of irrigation water? ……………………………………………… 40
6.7.3. Recirculating hydroponics systems…………………………………………………………. 40
6.7.4. Manipulation of environment and crop to reduce transpiration…………………………... 41
6.7.5. Conclusions: water saving in protected crops……………………………………………... 41
6.8. Outdoor (hardy) nursery stock………………………………………………………………………… 42
6.8.1. Background information: current status and drivers for change…………………………. 42
6.8.2. Types of growing beds and irrigation systems…………………………………………….. 42
6.8.2.1. Growing systems employing overhead irrigation or drippers………………… 42
6.8.2.2. Sub-irrigation growing systems.…………………………………………………. 42
6.8.3. Growing media………………………………………………………………………………… 43
6.8.4. Irrigation scheduling………………………………………………………………………….. 43
6.8.4.1. Scheduling based on estimates of evapotranspiration (ET)…………………. 44
6.8.4.2. Scheduling based on monitoring soil water content………………………….. 44
6.8.4.3. Scheduling based on imaging methods………………………………………… 44
6.8.4.4. Regulated deficit irrigation (RDI) ……………………………………………….. 44
6.8.5. Research facilities in the UK…………………………………………………………………. 44
6.8.6. Nursery-scale water management………………………………………………………….. 45
6.8.7. Knowledge transfer…………………………………………………………………………… 45
6.8.8. Conclusions: water saving in hardy nursery stock………………………………………… 46
7. Washing of Root Vegetable and Potato Crops………………………………………………… 47
7.1. The Washing Process………………………………………………………………………………….. 47
7.1.1. Dry soil removal…………………………………………………………………………….. 47
7.1.2. Dumping into packhouse………………………………………………………………….. 47
7.1.3. Soak tank and stone separation…………………………………………………………... 47
7.1.4. Rotary barrel washer………………………………………………………………………. 48
7.1.5. Brush washers and vegetable polishers (mainly carrots and parsnips)……………… 48
7.1.6. Hydrocooling (mainly carrots, parsnips and turnips)……………………………………. 48
7.1.7. Final spray rinse……………………………………………………………………………. 48
7.2. Water recycling and re-circulation……………………..……………………………..………………. 49
7.2.1. Waste water and solids disposal………………………………………………………….. 49
7.2.2. Screening……………………………………………………………………………………. 49
7.2.3. Sedimentation………………………………………………………………………………. 49
7.2.4. Waste soil/sludge…………………………………………………………………………… 49
7.2.5. Waste water………………………………………………………………………………… 50
7.2.6. Action Points to Minimise Water use in Washing Vegetable Crops…………………. 50
8. Current and emerging technologies aimed at saving water in livestock farming………………… 51
8.1. Water requirements of cattle………………………………………………………………………….. 53
8.1.1. Drinking water requirement……………………………………………………………….. 53
8.1.2. Drinking water supply………………………………………………………………………. 53
8.1.3. Wash water………………………………………………………………………………….. 55
8.1.4. Case studies on reduced water use……………………………………………………… 56
8.2. Water requirements of Sheep…………………………………………………………………………. 57
8.3. Water requirements of Pigs …………………………………………………………………………… 58
8.3.1. Drinking water requirement………………………………………………………………….. 58
8.3.2. Drinking water supply………………………………………………………………………… 58
8.3.3. Wash water……………………………………………………………………………………. 59
8.3.4. Water management on pig units……………………………………………………………. 59
8.4. Water requirements of poultry ……………………………………………………………………….. 60
8.4.1. Drinking water requirement………………………………………………………………….. 60
8.4.2. Washing water…………………………………………………………………………...... 60
8.5. Conclusions – water saving in livestock farming……………………………………………………. 61
9. Existing water saving initiatives and case studies……………………………………………………… 62
9.1. Award schemes…………………………………………………………………………………………. 62
9.2. Farmer-organised abstraction groups (FOAGs)…………………………………………………….. 62
9.3. Conclusions and opportunities………………………………………………………………………... 62
10. Opportunities to reduce water wastage on farms through auditing and good practice………... 62
11. Summary and conclusions: opportunities for water saving in agriculture………………………. 68
11.1. Drivers for water saving………………………………………………………………...……………… 68
11.2. Water withdrawals, changes in land use and food security…………….………………………..… 68
11.3. Reducing water withdrawals in over-abstracted catchments in England and Wales…………… 69